content: /* ===========================================================
   * JFreeChart : a free chart library for the Java(tm) platform
   * ===========================================================
   *
   * (C) Copyright 2000-2012, by Object Refinery Limited and Contributors.
   *
   * Project Info:  http://www.jfree.org/jfreechart/index.html
   *
   * This library is free software; you can redistribute it and/or modify it
   * under the terms of the GNU Lesser General Public License as published by
   * the Free Software Foundation; either version 2.1 of the License, or
   * (at your option) any later version.
   *
   * This library is distributed in the hope that it will be useful, but
   * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
   * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
   * License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with this library; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,
   * USA.
   *
   * [Oracle and Java are registered trademarks of Oracle and/or its affiliates. 
   * Other names may be trademarks of their respective owners.]
   *
   * --------------------
   * AbstractOverlay.java
   * --------------------
   * (C) Copyright 2009, by Object Refinery Limited.
   *
   * Original Author:  David Gilbert (for Object Refinery Limited);
   * Contributor(s):   -;
   *
   * Changes:
   * --------
   * 09-Apr-2009 : Version 1 (DG);
   *
   */
  
  package org.jfree.chart.panel;
  
  import javax.swing.event.EventListenerList;
  import org.jfree.chart.ChartPanel;
  import org.jfree.chart.event.ChartChangeEvent;
  import org.jfree.chart.event.OverlayChangeEvent;
  import org.jfree.chart.event.OverlayChangeListener;
  
  /**
   * A base class for implementing overlays for a {@link ChartPanel}.
   *
   * @since 1.0.13
   */
  public class AbstractOverlay {
  
      /** Storage for registered change listeners. */
      private transient EventListenerList changeListeners;
  
      /**
       * Default constructor.
       */
      public AbstractOverlay() {
          this.changeListeners = new EventListenerList();
      }
  
      /**
       * Registers an object for notification of changes to the overlay.
       *
       * @param listener  the listener (<code>null</code> not permitted).
       *
       * @see #removeChangeListener(OverlayChangeListener)
       */
      public void addChangeListener(OverlayChangeListener listener) {
          if (listener == null) {
              throw new IllegalArgumentException("Null 'listener' argument.");
          }
          this.changeListeners.add(OverlayChangeListener.class, listener);
      }
  
      /**
       * Deregisters an object for notification of changes to the overlay.
       *
       * @param listener  the listener (<code>null</code> not permitted)
       *
       * @see #addChangeListener(OverlayChangeListener)
       */
      public void removeChangeListener(OverlayChangeListener listener) {
          if (listener == null) {
              throw new IllegalArgumentException("Null 'listener' argument.");
          }
          this.changeListeners.remove(OverlayChangeListener.class, listener);
      }
  
      /**
       * Sends a default {@link ChartChangeEvent} to all registered listeners.
       * <P>
       * This method is for convenience only.
       */
      public void fireOverlayChanged() {
          OverlayChangeEvent event = new OverlayChangeEvent(this);
          notifyListeners(event);
      }
  
      /**
       * Sends a {@link ChartChangeEvent} to all registered listeners.
       *
       * @param event  information about the event that triggered the
       *               notification.
       */
      protected void notifyListeners(OverlayChangeEvent event) {
         Object[] listeners = this.changeListeners.getListenerList();
          for (int i = listeners.length - 2; i >= 0; i -= 2) {
              if (listeners[i] == OverlayChangeListener.class) {
                  ((OverlayChangeListener) listeners[i + 1]).overlayChanged(
                          event);
              }
          }
      }
  
  }
  
  